Bytebox

Bytebox is a WebAssembly VM.

Getting started

Requirements

Bytebox currently builds with Zig 0.12.x to avoid churn on zig master.

To run the tests:

• wasm-tools is required to run the wasm testsuite. You can install it via the rust toolchain cargo install wasm-tools or directly from the release page.
• clang v15.x+ is required to build the mem64 tests. However, if you don't have a compatible version of clang installed, you can pass --noclang to zig build to avoid the requirement.
• python3 is required to run the wasi testsuite. You may need to run python3 -m pip install -r test/wasi/wasi-testsuite/test-runner/requirements.txt to ensure the wasi test runner has all the necessary dependencies installed.

Run Tests

git clone --recurse-submodules https://github.com/rdunnington/bytebox.git
cd bytebox
zig build test-unit # run builtin zig unit tests
zig build test-wasm # run official wasm spec testsuite
zig build test-wasi # run official wasi spec testsuite
zig build test-mem64 # run memory64 compat test
zig build test # run all of the above in parallel (output will not be pretty!)

Usage

You can use the standalone runtime to load and execute WebAssembly programs:

zig build run -- <file> [function] [function args]...

Or embed Bytebox in your own programs:

// build.zig
const std = @import("std");

pub fn build(b: *std.build.Builder) void {
    const exe = b.addExecutable("my_program", "src/main.zig");
    exe.addPackage(std.build.Pkg{
        .name = "bytebox",
        .source = .{ .path = "bytebox/src/core.zig" }, // submodule in the root dir
    });
    exe.setTarget(b.standardTargetOptions(.{}));
    exe.setBuildMode(b.standardReleaseOptions());
    exe.install();
    const run = exe.run();
    const step = b.step("run", "runs my_program");
    step.dependOn(&run.step);
}

// main.zig
const std = @import("std");
const bytebox = @import("bytebox");

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    var allocator: std.mem.Allocator = gpa.allocator();

    const wasm_data: []u8 = try std.fs.cwd().readFileAlloc(allocator, "example.wasm", 1024 * 128);
    defer allocator.free(wasm_data);

    const module_def = try bytebox.createModuleDefinition(allocator, .{});
    defer module_def.destroy();
    try module_def.decode(wasm_data);

    const module_instance = try bytebox.createModuleInstance(.Stack, module_def, allocator);
    defer module_instance.destroy();
    try module_instance.instantiate(.{});
}

Inter-language FFI is also supported. See src/bytebox.h for an overview in C. To use bytebox as a static library, link with the built library in zig-out/lib/. Note that Zig assumes a default stack size of 8MB, so you'll need to ensure the same in your program.

Status

This project is still in the alpha stage.

Legend	Meaning
✅	Implemented
❌	TODO
💀	Not planned/Removed from spec

WebAssembly support:

Status	Feature
✅	WebAssembly 1.0
✅	Sign extension instructions
✅	Non-trapping float-to-int conversion
✅	Multiple values
✅	Reference types
✅	Table instructions
✅	Multiple tables
✅	Bulk memory and table instructions
✅	Vector instructions

WASI Preview 1 support:

Status	Feature
✅	args_get
✅	args_sizes_get
✅	environ_get
✅	environ_sizes_get
✅	clock_res_get
✅	clock_time_get
✅	fd_advise
✅	fd_allocate
✅	fd_close
✅	fd_datasync
✅	fd_fdstat_get
✅	fd_fdstat_set_flags
💀	fd_fdstat_set_rights
✅	fd_filestat_get
✅	fd_filestat_set_size
✅	fd_filestat_set_times
✅	fd_pread
✅	fd_prestat_get
✅	fd_prestat_dir_name
✅	fd_pwrite
✅	fd_read
✅	fd_readdir
✅	fd_renumber
✅	fd_seek
❌	fd_sync
✅	fd_tell
✅	fd_write
✅	path_create_directory
✅	path_filestat_get
✅	path_filestat_set_times
❌	path_link
✅	path_open
❌	path_readlink
✅	path_remove_directory
❌	path_rename
✅	path_symlink
✅	path_unlink_file
❌	poll_oneoff
✅	proc_exit
💀	proc_raise
❌	sched_yield
✅	random_get
❌	sock_accept
❌	sock_recv
❌	sock_send
❌	sock_shutdown

Roadmap

These tasks must be completed to enter alpha:

• API ergonomics pass
• Documentation
• General TODO/code cleanup
• Crash hardening/fuzzing

To enter beta:

• No breaking API changes after this point
• Performance competitive with other well-known interpreters (e.g. micro-wasm-runtime, wasm3)

To have a 1.0 release:

• Tested with a wide variety of wasm programs
• Successfully used in other beta-quality projects